This program seeks to determine the mechanisms responsible for toxicities associated with acellular hemoglobins (Hbs) in blood and to establish strategies to prevent or reverse these toxicities. The results will have a significant impact on hematology and transfusion medicine by: (1) providing rational therapies to minimize the clinical problems associated with Hb released from autologous, hemolyzed red blood cells in patients with chronic or acute diseases and from heterologous stored blood used for transfusions and (2) Identifying the underlying causes of the commercial failure of extracellular Hb-based oxygen carriers (HBOCs), providing strategies to mitigate or eliminate these problems, and optimizing their efficacy for volume expansion and tissue perfusion with reduced toxicity. A long term goal is to provide safer and more effective blood transfusions using therapeutic options that match transfusion strategies with clinical needs and availability of fresh stored blood. These objectives will be achieved through 3 projects, and 4 core facilities. Project 1 (UCSD, M. Intaglietta, PI) wil use microvascular perfusion markers to identity Hb-related changes in capillary function and examine Hb toxicity during acute and chronic vascular dysfunction. Project 2 (Rice U., J. Olson, PI and A. Alayash, FDA) will engineer recombinant Hb with varied (high/low) 02 binding, NO dioxygenation, oxidation, and denaturation properties and use them to test the importance of NO scavenging, oxidative degradation, denaturation and precipitation, and impaired clearance in causing plasma Hb toxicity in cellular, organ, and whole animal model systems. Project 3 (AECOM, J. Friedman, PI) will evaluate whether PEGylation or polymerization of Hb, generation of bioactive NO by Hb, injection of nanoparticles releasing NO or GSNO, and the infusion of reducing agents and haptoglobin can be used effectively to limit toxicity derived from the oxidative reactions of acellular Hb. The four Cores are: Core A, Administrative unit (AECOM, Friedman, PI); Core B, HbA Chemical Modifications and Nanoparticle Production (AECOM, Nacharaju, leader); Core C, Recombinant HbA Production for In Vivo Toxicity Studies (Rice U. Olson, leader); Core D, Chemical, Cellular, And Animal Toxicity Evaluations (FDA, Alayash leader)